What Is Fork Performance?

[cachagua]

In another thread, someone talked about replacing a Time carbon fork with a Ritchey, and finding that its performance was a lot better. I'm riding a Time now, which was a radical improvement over the bike's original fork -- although I attribute a lot of that to more appropriate rake. The Ritchey's rake is the same as the Time's -- so how much MORE better is it? And better how?

What I'm really asking is, what constitutes performance, when we're talking forks? Not just "correct" geometry, that's simple -- but what does a fork do that makes you tell your friends what a fantastic fork you've got?

[Louis]

I'd guess stiffness vs comfortable ride, and the correct balance of the two for the intended use of that particular bike.

[cachagua]

So, less stiffness = more comfort?

Could it be that simple?

[Louis]

So, less stiffness = more comfort?

Could it be that simple?

I'm sure the details are more complicated, but too much stiffness (and 110 psi tires) is certainly not comfortable over time. And too little stiffness isn't good either.

Caveat: I'm not a framebuilder

[parris]

I think that the "better" part of the different fork is what needs to be figured out. what is it that the bike owner felt would be improved with a different fork?

several builders put a lot of effort into designing the fork to work well with the frame that they build for the client because the fork is so critical to the overall performance and feel of the bike.

[eddief]

I have owned more than 30 bikes over the last many years. I can tell ya each felt slightly different, but could never attribute the difference specifically to one fork or the other. Lots of variables in the overall performance and feel of a bike. But I do believe another person, not me, who rides bikes to the limit would be able to qualify, not quantify, one fork over the other.

And it would be interesting to take one frame and test it to the limit with different forks.

I bet Dave Kirk knows.

One vid is worth a 1000 cringes and would suggest at least different materials react differently to different sorts of inputs:

https://www.youtube.com/watch?v=nvk63bmVpck

More scientific:

https://www.youtube.com/watch?v=lrjId0-K-Ts

[nooneline]

Any anecdote is going to be pretty subjective and rely on imprecise perceptions and uncontrolled variables. But, like others, I've ridden the same setup but with different forks.

To me, a better fork has the following characteristics:
*a more muted, softer ride, plus reduced chattering/flex during hard braking (think emergency brakes at 50+mph descents)
*more confident diving into corners (think screaming crit corners curb-to-curb at 35+ mph) - solid wheel adhesion (worse forks will flex and twitch in the wrong ways)
*Light

Taken together all that sounds like a combination of stiffness where it's needed and not-stiffness where it's not needed - like what Louis said. Or, as the chestnut says, vertically compliant but laterally stiff...

[bobswire]

In another thread, someone talked about replacing a Time carbon fork with a Ritchey, and finding that its performance was a lot better. I'm riding a Time now, which was a radical improvement over the bike's original fork -- although I attribute a lot of that to more appropriate rake. The Ritchey's rake is the same as the Time's -- so how much MORE better is it? And better how?

What I'm really asking is, what constitutes performance, when we're talking forks? Not just "correct" geometry, that's simple -- but what does a fork do that makes you tell your friends what a fantastic fork you've got?
That was me that replaced a Time fork,this was not a knock against the Time fork, just my personal subjective opinion on its handling capabilities in regards to my uses.
I was responding to someone wanting to replace a "1 inch" fork on a Cervelo Prodigy. Having had a Prodigy,I exchanged a time fork for a Ritchey because I wasn't comfortable with the time in descending. I could vouch for the Ritchey being a bit more stable while descending which in turn gives you more confidence. I live in San Francisco, hills and climbs galore in and around this great city. Having a fork that is not too noodly and tracts well is a prerequisite of mine.
No science was involved in my study, just a seat of the pants observation.
BTW I was only talking about readily available 1" forks. Reynolds are nice too but difficult to come by. Wound Ups are great too, IMO the best out there if you can get by the looks.

http://i40.tinypic.com/4kzptt.jpg

[tv_vt]

Well, let's see. Things I've noticed about forks on different bikes, and different forks on the same bike:

Stiffness - there's stiffness in the legs of the fork, and stiffness in the steerer tube. Stiffness in the steerer tube is paramount - if it's noodly, you'll notice every time you stand on the pedals, or when sprinting. IMO, a noodly fork is god-awful and can be pretty frightening in a big sprint. Yet if you don't ride hard, it can give a pretty soft ride that you might like.
Stiffness in fork legs can be overdone - too stiff and bike turns into a bone-rattler. Also there's straight ahead stiffness and side-to-side stiffness, which will show up on those tight downhill curves.

Weight - an obvious one, but maybe not too important once we're comparing same materials. Steel vs carbon, there's a huge difference, though.

Rake - I've found this to make a huge difference. I have been gravitating to geometry with longer trail lately, and going to fork rakes that give me 60-62mm of trail.

Clearance - for larger tires seems to be a sought-after feature these days.

Looks - some forks just plain look fantastic, and others don't (atmo).

Dropouts - all carbon, titanium, or aluminum, or steel. Do any perform better? - have no idea.

My fav forks currently: Edge/Enve 2.0 40mm rake, Seven 5E medium reach, Look HSC5. And if I could wrap my head around the cost, the Serotta F3/S3 6.5/8.5 is beautiful, too. I'd love to put a 40mm F3 6.5 on my Fierte IT, but the Edge is working out really well. To me, more muted is not the go-to feature. Rather, it's 'crispness,' some stiffness but with some muting, and the stiffness stays there when I stand up and hammer, instead of any kind of mushiness.

FWIW, I'm 6'2" and use about 300mm steerer tubes.

[David Kirk]

Forks can vary in any number of ways........just like a frame I suppose.

Assuming that the fork is properly aligned (NOT a safe assumption with some out-of-a-box forks - some are dead on and others are really bad) and that the rake is an appropriate match to the head angle to give the desired trail the rest of it comes down to stiffness.

The important thing to remember when it comes to stiffness is that more isn't always better. Just like the Goldy Locks thing a fork can be too soft, too stiff or just right.

Forks flex a given amount just like every other part of the bike and they flex in every direction - fore/aft, laterally, in twist, and to a lessor degree up/down (compression end to end).

The directions of flex that really can give the bike a good or bad feel are mostly lateral and twist as they can give the bike a nice crisp and predictable steering/handling feel or they can make the bike feel vague and unpredictable if they move too much.

What is too much? Hard to say and even harder for most to measure but in the end it's not all that hard to feel if you 'listen' to what the bike feels like. It will of course depend on how the bike is used and who much the rider weighs and to a certain extent how tall the rider is (tall guys having a higher COG and applying more leverage to the fork).

I've been told by some that structures like frames and forks don't actually flex, or at least they the amount they flex isn't meaningful, and that just seems crazy to me. All one needs to do it sit on the bike with your feet on the floor, lock the front brake and rock the bike fore/aft HARD and watch everything move. The fork blades will flex fore/aft a lot, the steerer will flex and even the top and down tubes will arch some making the head angle steeper when you push the bike forward. Watch someone else do this from the side and it's crazy how much even the stiffest set ups move.............and the important thing to remember is that this is natural and to a certain degree a good thing. Goldy Locks again.

I realize the above is in no way an 'answer' and this is largely because there isn't a clean and simple one - I wish there was.

dave

[cachagua]

No, that's an excellent answer, and you were one of the people I was hoping to hear from, because if I remember right from your web site, there's a fork you'll only put on some of your bikes, and it isn't available with others? And thanks also to bobswire, I think it was indeed you who got me thinking about this.

My own observations are that long ago I had a poorly-chosen fork (Kestrel EMS) pretty well ruin what should have been a fantastic bike (Merlin Extralight), and more recently I had a fork (the Time) completely transform a bike (a Corsa Extra) and turn it from a dog into a really sublime ride.

My current problem is more like the former: I have a lovely Colorado CRL which ought to be sublime, but it rides like a dog. I'd swap the fork without hesitation, except that in the other two cases the rake was the (main) problem -- both the Kestrel and the original fork in the Merckx have more rake than the Time that's in the CE now.

Whereas the Time and the Ritchey both have the same rake as the CRL's fork. So do I reduce the rake still further? Do I shoot for more steerer rigidity and flex reduction with the Ritchey or another option? Do I ditch the CRL and buy the Luigino that someone's got in the Classifieds?

I'm not necessarily expecting a definitive answer to those questions, it's just the shape of what I'm wondering. But I welcome anyone's input.

[tv_vt]

Do I ditch the CRL and buy the Luigino that someone's got in the Classifieds?

Well now, that's easy to answer! Duh!

[cachagua]

Ha! Yes. . .

Easy to answer, a little harder to pay for.

Maybe the guy would trade me straight across?

[carpediemracing]

I was in the "all forks are about the same" boat until I got my (cough cough) SystemSix with its tapered steerer tube fork. The bike was noticeably easier to control when cornering at the limit in high speed (to me) sweepers. I don't do any crazy descents so for me a fast sweeper would be a local road with a blind 45 mph right-hand curve.

On my prior TCRs (with the stock "less aero" blades or with a Reynolds Ouzo) the bike would not respond and I'd end up on the yellow line or worse.

I replaced the original aero blade fork off my TCRs (I eventually had 3) immediately because the forks were so flexible fore/aft that I literally didn't have confidence that the fork wouldn't break. I think I could get the axle to move about 3" total fore/aft relative to the frame.

When I got my fork-less Tsunami I put the Ouzo in there. Fine. My next Tsunami got a 3T Team. Much closer to the SystemSix in front end feel but lacking a bit in lateral rigidity. I got the original Tsunami modded and put an ENVE 2.0 fork. Seemed similar to the 3T Team.

After my experiences with the forks I decided that I want, above all, incredible lateral rigidity, i.e. side to side, with a frame that supports that. The SystemSix was just incredible when blasting into a hard corner or curve. I want a reasonably stiff fore/aft fork as well, not like the rubbery TCR forks (the slimmer forks seemed to be better than the original bladed-style forks).

I want that lower race to be pretty well fixed, no slop/movement, with a head tube and downtube to support that non-movement. The top race can move a bit fore/aft I guess (flexing the frame tubes, allowing the steerer to move a touch), the bottom though needs to stay put. If the front wheel doesn't change its lean angle without me saying so then I'm happy. The "flexible" forks seem to allow the wheel to lean more or less in some arbitrary way, causing the bike to go off line. That's the impression I have when I ride, I have no idea if I've translated it properly to actual frame dynamics.

My ultimate frame would have a front end with a tapered steerer with a 1.5" lower race. I'd use the fork out of my SystemSix or one like it if I could.

[jzisk]

Stiff doesn't always translate into accurate, trustworthy cornering for a fork, and rake obviously only factors in as a part of the complete geometry... I have 5 serious rides, all with slightly different geometry, and having played with many forks on the 3 that allow easy switching out, I'd say geometry and tubing diameter trump all, as far as comfort and handling are concerned. Fork "performance", beyond a point of quality, seems like a placebo effect. My faves-- Ouzo Pro, Columbus Minimal, Serotta F3, Falz... But I dare you to try a blind-test. Betcha I'd fail it.

[DHallerman]

Wound Ups are great too, IMO the best out there if you can get by the looks.


I love Wound Up forks -- for performance and, yes, for looks too.

HOWEVER, the Wound Up is a stiff fork. So I only love them on my 1990s-era titanium frames, which are kinda springy. Works as a great complement.

BUT, when I tried a Wound Up on an Ibis steel frame, did not like it at all. The whole bike was too stiff, and it's not like the Ibis steel is super-stiff by itself, but the combo just did not work for me.

Dave, who replaced that Wound Up on the Ibis Spanky with a Ritchey Comp and has been much happier

[sandyrs]

Back from the dead!

[Joachim]

Back from the dead!

We need smilies for these...

http://www.gomotes.com/emoticon/zombie.gif

[benb]

I've never really swapped forks on the same bike but have tried a pretty wide range of bikes with different style forks.. All are noticeably different for me.

2 Trek forks that were steel steerer tube + carbon legs/crown w/very similar frames (both trek aluminum) Stiff enough and no real problem with either of them.. one of them had curved legs and was probably more comfy. Both were fine in cornering. One was 1", one was 1 1/8".

Giant all carbon fork 1 1/8" (2004) - Clearly not stiff enough in some way. Comfy, but noticeable flex in cornering.

Serotta F3 - seemed to be just about perfect in my memory.

Enve/Edge 1 1/8th -> 1 1/4" - Similar in most ways to the F3 but more crisp turn in

All Steel on my current bike 1 1/8 (cheap fork).. not stiff enough for canti brakes, maybe some slight issues even with the current V-brakes I have. Cornering is fine but not as crisp. Noticeably harsh, probably because it is built to carry 30lbs on a front rack. Harsh despite a generous curve to the fork legs & bigger tires.

I have a pretty strong recollection of all-steel MTB rigid forks back in the 90s.. nothing fancy but most of the ones I rode did not have enough stiffness to handle hard braking.

[berserk87]

Forks can vary in any number of ways........just like a frame I suppose.

Assuming that the fork is properly aligned (NOT a safe assumption with some out-of-a-box forks - some are dead on and others are really bad) and that the rake is an appropriate match to the head angle to give the desired trail the rest of it comes down to stiffness.

The important thing to remember when it comes to stiffness is that more isn't always better. Just like the Goldy Locks thing a fork can be too soft, too stiff or just right.

Forks flex a given amount just like every other part of the bike and they flex in every direction - fore/aft, laterally, in twist, and to a lessor degree up/down (compression end to end).

The directions of flex that really can give the bike a good or bad feel are mostly lateral and twist as they can give the bike a nice crisp and predictable steering/handling feel or they can make the bike feel vague and unpredictable if they move too much.

What is too much? Hard to say and even harder for most to measure but in the end it's not all that hard to feel if you 'listen' to what the bike feels like. It will of course depend on how the bike is used and who much the rider weighs and to a certain extent how tall the rider is (tall guys having a higher COG and applying more leverage to the fork).

I've been told by some that structures like frames and forks don't actually flex, or at least they the amount they flex isn't meaningful, and that just seems crazy to me. All one needs to do it sit on the bike with your feet on the floor, lock the front brake and rock the bike fore/aft HARD and watch everything move. The fork blades will flex fore/aft a lot, the steerer will flex and even the top and down tubes will arch some making the head angle steeper when you push the bike forward. Watch someone else do this from the side and it's crazy how much even the stiffest set ups move.............and the important thing to remember is that this is natural and to a certain degree a good thing. Goldy Locks again.

I realize the above is in no way an 'answer' and this is largely because there isn't a clean and simple one - I wish there was.

dave

OK - not to sound like a toady or bum-smoocher, but that's the best explanation I have ever read on the elements of fork performance. That was clearly stated and well-written. Thanks - Mike